This invention relates to assays and more particularly to immunoassays for the detection of antigens.
Presently, immunoassays are capable of detecting only one antigen (if the antibody is cross-reactive, the assay might detect a set of chemically similar antigens). If there are chemical species present in the sample which affect the affinity of the antibody for its antigen (interferants), the results of the assay will change. If the sample is an unknown, there will be no way of realizing that the results of the assay have been compromised. For example, the commercially available immunoassays for petroleum in water use a single conventional test such as a competition immunoassay, to give the petroleum content of water for concentrations in the ppm (parts per million) range. The antibodies in these assays bind a specific constituent of the petroleum, usually BTEX (benzene, toluene, ethylbenzene, and xylene). However, petroleum contains other species (such as alkanes) that change the antibody affinity for the BTEX, and thus change the results of the assay. In the protocol recommended by the manufacturer of these kits, the calibration is performed against a specific petroleum product (i.e., gasoline, kerosene, home heating fuel, etc). This assumes that one knows before hand what type of petroleum product is in the sample. If not, the result of the assay is inaccurate. A modification of the technique to quantify the interferants would be extremely valuable in obtaining additional quantitative information from the assay.